Microwave systems such as microwave waveguide systems and microwave plasma processing systems may use windows to isolate parts of the systems. In plasma processing systems, microwave energy can be used, for example, to create a plasma such as in Electron Cyclotron Resonance (ECR) systems, to pump process gases such as in a plasma pump and/or to allow access to microwave plasma diagnostics. In these plasma processing systems microwave windows are used to separate a processing chamber, which can be under high vacuum, from an incoming microwave waveguide, which can be at atmospheric pressure.
In plasma processing systems, the microwave window is installed on a wall of the process chamber at the place where microwave energy is delivered to the process chamber. The microwave window is usually made of ceramic dielectric materials, such as alumina (Al2O3), aluminum nitride (AIN) and PTFE (Teflon).